Range measuring system



Feb. 16, 1954 J, R, MQORE RANGE MEASURING SYSTEM 5 Sheets-Sheet l FiledMay 19, 1944 INVENTOR. JAMES R. MOORE.

TTOHNEK Feb. 16, 1954 J. R. MOORE RANGE MEASURING SYSTEM 5 Sheets-Sheet2 Filed May 19, 1944 INVENTOR. JAMES R. MOORE.

ATTORNEY NOE Feb. 16, 1954 1 R, MOORE 2,669,711

RANGE MEASURING SYSTEM Filed May 19, 1944 5 Sheets-Sheet I5 INVENTOR.JAMES R. MOORE.

ATTORNEY Feb. 16, 1954 J. R. MOORE RANGE MEASURING SYSTEM 5 Sheets-Sheet4 Filed May 19, 1944 OUTPUT OF OF AMPLIFIER I7, FIG. 1.

I`| I`| N I`l I OUTPUT oF |,J 1,1 [,J l/l MuLTlvlBRAToR 300,302,416. 3.

OUTPUT OF BUFFER AMPLIFIER 304.

OUTPUT 0F FREQUENCY DIVIDER 3|Ol 3I2.

OUTPUT OF FILTER 3I4, 3I5.

OUTPUT OF MIXER 402.

L@ m4 TR NE om CM NF 00 S Mm Nm mN SE Tm UC PS mD N A OUTPUT OF EXPANDER434.

OUTPUT OF SHAPING AMPLIFIER 436 OUTPUT OF SAW TOOTH GENERATOR 43B.

u OF TUBE 454. MEASURING CIRCUIT) COMBINED RANGE MARKER AND SWEEP WAVE.

CONTROL GRID AND SCREEN GRID SIGNALS OF MIXER 404.

Ns. OM M D E 4 oon m R m Pm M mm F LG o MH T u mm .m SO T u m o Rm GSOUTPUT OF SAW' TOOTH GENERATOR 4|8..

OUTPUT OF TRANSMITTER IO, FIG.1.

INVENTOR. JAMES R. MOORE.

A T TORNEI( Feb. 16, 1954 J. R, MQQRE 2,669,711

RANGE MEAsuRING SYSTEM Filed May 19', 1944 l 5 Shee'ts-Sheet 5 "I lll[any AAAAA INVEN TOR. JAMES R. MOORE.

BY MQMLM ATTORNEY Patented Feb. 16, 1954 UNITED S TATE FFICE (Grantedunder Title 35, U. S. Code (1952),

sec. 266) la Claims.

This invention relates to a radio system for determining the location ofobjects and a methd and means for determining slant range of objectsdetected by such system.

In the radio-object locating systems of this type, a pulse of ultra-highfrequency is radiated by a highly directional antenna, the radiatedpulse acting as an exploratory pulse of the system. If the transmittedexploratory pulse strikes an object capable of reradiating the radiofrequency Waves, it will be reiiected in part, back to its source bythis object, thus producing a radio frequency echo signal. This echopulse, on its return to its source, may have suicient energy to producean observable eiiect in a suitable receiver located in the vicinity ofthe original source of the exploratory pulses. Generally the eilectconsists of visual indications on a cathode-ray oscilloscope in a formof vertical, upwardly projecting peaks from a horizontal time-base line.Such representation of echoes is known as class A representation. Thesevisual indications, together with the angular position of the antenna,are utilized for determining the location of the echo-producing objects.Depending upon the number and type oi the receivers used in connectionwith the systems of this type, it is possible to obtain azimuth,elevation, slant range, and horizontal range of the objects. Theinvention relates to a new method and apparatus for determining theslant range of the objects.

Generally, all radio locators determine the slant range by measuring thetime interval between the transmission of the exploratory pulse and thereception of the echo signal, and converting this interval into lineardistance, the two being proportional to each other because of constant,known velocity or" propagation of the radio waves which is equal to thespeed of light. This time interval is measured by using electricaloscillations and electrical circuits which are capable of transformingthe electrical oscillations taking place during this interval of timedirectly into units of distance. The distancemeasuring electricalcircuits which are used for range determinations are, as a rule, eithera phase shifter capable of giving 360 phase shift, or a resistancenetwork, both of which may be calibrated so as to give the rangedistance to an echo-producing object directly in miles when the desiredsignal is properly positioned with respectlto some appropriate referenceline or a marker appearing on the screen of the range oscilloscope. I nsome systems the `field of signals reproduced on the screen oi the rangeoscilloscope remains stationary, and the marker signal is moved acrossthe eld until it appears directly in line with the desired signal; whenthis is the case, the range of the object producing the selected echomay be read directly on the dial of the phase shifter or resistancenetwork either of which may be used for shifting the lateral position ofthe selected echo or of the marker on the screen of the rangeoscilloscope.

One of the factors limiting the accuracy of range determinations in thesystems of this type is the accuracy of the electrical circuits, i. e.,the phase shifter or the resistance network, which are used formeasuring the time interval between the transmission of the exploratorypulse and the reception of the echo from the object under observation.Thus the accuracy of the phase Shifters, which are used for shifting thephase of a sinusoidal wave instrumental in measuring the above-mentionedtime interval, is ordinarily in the order of $1.5", or a total possibleerror of 3. Thus the phase shifter may introduce considerable error inthe range determinations when it is used in connection with long rangeradio object-locating systems. Systems have been devised which employtwo phase Shifters, one of which is used for shifting the phase of afundamental sinusoidal wave, and the other for shifting the phase of aharmonic of said wave, the latter controlling the timing of the sweepcircuits of the Oscilloscopes, and, as a consequence, controlling theaccuracy of the range determinations. The error introduced by the phaseShifters in the systems of this type is reduced by a factor equal to thenumber of the harmonic used for controlling the oscilloscope circuits.The saine type of accuracy limitations apply to the electrical deviceswhich use resistance networks for range determinations, and, as aconsequence, the resistance networks are also capable of introducing aconsiderable error in the range determinations when they are used inconnection with long range radio object-locating systems.

The invention discloses a new method and apparatus for obtaining moreaccurate range determinations in connection with the long-range radioobject-locating systems using resistance networks for this purpose. Tworange oscilloscopes are used in connection with the range channel, oneof the Oscilloscopes reproducing on its screen the full range of thesystem, and the other osciiloscope, called high velocity oscillo- Scope.in this specification, reproducing only a fraction or a sector of thefull range. Greater accuracy of range determinations is accomplished byusing a resistance network for measuring only a small portion of therange under investigation at any given time, thus reducing the possibleerror in the range determinations. In the prior Systems, which usesimilar type of resistance networks for range determinations, thenetworks must have suiiicient resistance for measuring any range fromZero to full range of the system, and since the possible error increaseswith the distance, it follows that the error increases with the increasein range.

The invention limits this increase in error by limiting the rangedetermination assigned to the resistance network only to a fraction, ora sector, of the total range, and by providing additional circuits forselecting the desired range sector, the latter circuits being arrangedso that they do not introduce any additional error of their own into therange determinations.

To accomplish theselection of any particular range sector the system isprovided with a phase shifter which enables one to select and reproduceany desired portion of the full range on the screen of the high velocityoscilloscope. Since the operation of the phase shifter does not resultin the introduction of any additional errors into the rangemeasurements, the accuracy of the range determinations, is therefore,limited only by the accuracy of the resistance network.

It is, therefore, an object of this invention to provide a method andmeans for determining with high degree of accuracy the range of olojectsby means of radio obiect-locating systems where range determinations areperformed by means of resistance networks.

Another obiect of this invention is to `provide a radio obiect-locatingsystem equipped with a vrange measuring resistance network, the resistance of this network in terms of range being equal only to afraction of the total range of the system, and the accuracy of rangedeterminations of the system being limitedonly by the accuracy of theresistance network.

Another object of this invention is to provide a radio object-locatingsystem in which higher accuracy of range determinations is made possibleby providing a resistance network capable of 'measuring only a portionof thetotal range. and

combining this resistance network with a phase shifter for selecting thedesired portion of the total range.

Still an additional object 4of this invention is to provide a radioobject-locating system capable of reproducing the full range of thesystem on `the screen of one oscilloscope, and the desired portion ofthe full range on the screen of the other range oscilloscope with ,afaster sweep.

An additional obiect of this invention is to provide a positivesynchronous operation of the transmitting and receiving channels; strictsynchronism between the channels is necessary since the accuracy of allrange determinations is aiflected by the synchronization of the twochanne s.

Yet another object of this invention is to provide a range measuringdevice which combines the range determining resistance .network and aphase shifter for selecting the desired portion of the total range, saiddevice being so `constructed and arranged that the sought range readingappears as a single reading on a single dial.

The novel features which I believe to be characteristic of `my.inventionareiseixfcltth with particularity in the appended claims. Myinvention itself, however, both as to its organization and method ofoperation, together with further objects and advantages thereof may bestbe understood by reference to the following description taken inconnection with the accompanying drawings in which:

Figure 1 is a block diagram of the radio objectlocating system,

Figure 2 illustrates the relationship o f Figs. 3 and i with respect toeach other for their proper reading,

Figures 3 and 4 are the schematic diagram of the high velocity and fullrange Oscilloscopes, and

`of the range determining circuit,

Figure 5 illustrates the oscillograms of signals appearing in thecircuits disclosed in Figs. 1, 3,

,and f 4,

Figures 6 and 7 illustrate typical signal patterns appearing upon thescreens of the full range `and high velocity Oscilloscopes respectively,

Figure 3 is an exploded isometric view of some of the elements of thephase shifter and the resistance network used for determining range.

For the sake of clearness the same reference vcharacters are used in theseveral figures where the elements thereof are identical to the elementsillustrated throughout the several figures.

Referring now to Fig. 1, a transmitter I0 appears in the upper leftcorner of the block diagram; a receiver I2 is positioned in line andbelow the transmitter-keyer combination; the full range oscilloscopetube I4 is in the lower left corner of the diagram; the high velocityoscilloscope tube I6 is to the right of the full range tube, and amaster oscillator and shaping amplier I7 which is used for synchronouslyoperating `the transmitting and the receiving channels, appears in theupper right corner of the diagram.

Proceeding now with the description of the transmitting channel, itbegins at the master oscillator and shaping ampliiier Ii'l whichcontrols a square wave generator IS, the former `generating asubstantially rectangular wave 5--0 Vand the `latter a series of pulses5-I. 'Signal oscillograms shown in Fig. 1 are also illustrated in theirproper time relationship in Fig. 5 where they bear the same numerals.lThe master oscillator is preferably of the magnetostriction type andtemperature-controlled. The frequency -of the master oscillator ismaintained constant to improve the accuracy of all range determinationswhich kare beyond the first sector. The sinusoidal wave generated by themaster oscillator is impressed on one or several stages of the shapingamplifier which consists of overdriven vacuum tubes transforming thesinusoidal wave impressed upon them into a substantially rectangularwave 5 0. The shaping amplifiers may be omitted altogether when lessaccurate range determinations may be tolerated; however, more accuratetiming of the square wave generator I8 may be obtained when the shapingamplifier is interposed between 'the master oscillator and thesquare-wave generator I8, so that the latter is timed by the signalshaving steeper wave-fronts than the sinusoidal wave.

Square wave generator I8 comprises la modified Eccles-Jordanmultivibrator circuit generating rectangular pulses 5-I which areimpressed on a buffer amplifier 20, the output of which is impressed ona frequency divider 22 and mixers 28 and 48, over conductors 29 and 35respectively. The frequency divider 22 represents a kmultivibratorcircuit which reduces the frequency lof vthe square Wave generator I8 byan appropriate fac'- .of this tube.

tor, such as four in an example described in this specification, so thatthe period of pulses 5 3 appearing in the output circuit of thefrequency divider is four times longer than the period ci pulses 5 1 Thevoltage pulses 5 3 are impressed on a filter 2t consisting of aplurality of resistance-condenser combinations which transform them intoa sinusoidal wave E li the period of which is equal to the period of thefundamental wave component of wave 5 3. The output of filter 24 isimpressed on a sinusoidal wave amplier 26 which impresses it on mixer 28and a phase shifter 3d. In the illustrated example, the mixer consistsof a properly biased multigrid vacuum tube which suppresses thesinusoidal wave impressed on its screen grids and the rectangular pulses5 2 impressed on its control grid except the rectangular pulses 5 2which coincide in time of their occurrence with the occurrence of thepositive maximum crests of the sinusoidal wave on the screen grid of themixer, as illustrated at 5 i2 and 5 i3 in Fig. 5. Acn cordingly, theoutput oi the mixer consists of a series of pulses E l, the periodicityof which is such that they coincide in time with the occurrence of everyfourth rectangular pulse 5 2. The selected pulses 5 i3 are impressedover a conductor 32 on a keyer 34 where they are transformed into keyingpulses used for keying transmitter l0. Transmitter It transmits over ahighly directional antenna array 35 a continuous series of exploratorypulses ii-i t used for detecting the position of those objects locatedin the field of the antenna lobe which are capable of reradiating thetransmitted energy.

The reradiated energy is received by an antenna array 33 which isconnected to receiver i2, the latter, after proper amplification of thereceived signals, impressing them over conductors 39 and 40 on thevertical deiiection plates of the full range and high velocity rangeoscilloscope tubes I4 and I6.

The block diagram discloses two separate antennae, 36 and 38. There aresystems now in use which have separate transmitting and receivingantennae, as indicated in Fig. l, as well as the systems which use oneantenna to transmit as well as to receive the signals, with a duplexingcircuit interconnecting transmitter-receiver con bination to the sameantenna. The disclosed range determining system may function equallywell with either oi the two systems.

A sweep circuit d2 of the full range tube I4 is connected to the outputof mixer 2S, the latter controlling the timing of the sweep wave 5 l5appearing in the output of sweep circuit d2; the sweep wave 5 l5 is sotimed that one horizontal sweep is produced on the screen of the fullrange tube i4 between the successive transmitted pulses E Ii so that theentire, full range for which the system is designed is reproduced on thescreen One of the intensity grids of this oscilloscope, i. e., anintensity grid dt, is connected over a conductor il to the output of anexpander 5t; the function and the purpose of this connection will bedescribed later in connection with the description of the circuitsconnected to the high velocity tube I5.

Proceeding now with the description of circuits of the high velocitytube l5, they begin with a phase shifter '30 which is connected to theoutput of amplifier 25. In the example selected for illustrating morespecically the invention, phase shifter 3,'3 is so constructed that itmay produce 0, 90, 180, and 270 phase respectively.

shifts in the sinusoidal wave 5 5 impressed upon it by amplifier 25.Sinusoidal wave 5 5 appearing in the output of phase shifter 30 isimpressed in series on an amplier and a mixer 48, the functioning of thelatter being identical in all respects to the functioning of thepreviously described mixer 28; it selects every fourth rectangular pulse5 2 impressed upon it by the buffer amplifier 2d, the selection beingaccomplished with the aid of the sinusoidal wave 5 5. The selectedpulses 5 6 are expanded in an expander 50 which transforms them into aseries ci substantially rectangular pulses 5 7 whose ilat tops are twiceas wide as the width of pulses 5 2. The rectangular pulses 5 1 areimpressed on a sweep circuit 5i? where they control the generation of ahigh velocity saw-tooth wave 5 9 which is used for producing horizontalsweep in tube It. The sweep circuit 52 is adjusted so that the durationof the linear portion of the saw-tooth wave is equal to the duration ofthe rectangular` wave 5 7. The rectangular pulses 5 7 are also impressedon the intensity grids 5d and d4 of the cathode ray tubes i5 and I4Normally the electron beam, because oi the blocking biasing potential,does not reach the screen of tube lli and the positive rectangular wave5 1 is used in this tube for overcoming this blocking potential.Accordingly, only the echoes reaching the high velocity tube at thisinstant are reproduced on its screen. In tube l!! the rectangular pulsesE 'l make the signals reproduced on its screen at this instant appearbrighter than the remaining iield, thus indicating at tube ill the rangesector reproduced on tube |63.

The output of the sweep circuit 52 is also connected to a rangemeasuring circuit 5t, which has as one of its component parts thepreviously mentioned resistance network used for determining the range.The functioning of the range measuring circuit 56 will be described morefully in connection with the description of Figs. 3, 4, and 8. Sufficeit to say at this time that it impresses a rectangular wave 5 i0 on thevertical plate 5B of tube it thus producing a vertical step wil, Fig. 7,on a horizontal time-base line of this tube. This vertical step may belaterally displaced until it coincides with the leading edge of thedesired echo signal, and when this is the case, the dial of the rangemeasuring circuit indicates the slant range to the object producing thisecho.

Before proceeding with the detailed description of the schematicdiagrams of the range determining system, a brief functional cycle ofthe system disclosed in Fig. l will be given. vlirorn the descriptiongiven thus far, it follows that the transmitting as well as thereceiving channels are under continuous control of the master oscillatoril, this oscillator ccntrolling the time intervals between thesuccessive exploratory pulses in the transmitting channel, and properlateral positioning ci the received signals on the time-base lines ofthe oscilloscope tubes. The latter step is accomplished by controllingthe sweep circuits of the two tubes by means of the control pulses 5 1and 5 l3, both of which are obtained by selecting every fourth pulsegenerated by the square wave generator i8 in the described example. Theposition of the horizontal base line of tube lll remains permanentlyfixed, in terms of time, with respect to the transmitted exploratorypulse E I, since the same pulse 5 I3 is used for controlling thetransAmitterzasfwellgas 'the sweep circuit 42. flhlsxtllbe reproduces theAfull range of the system, as illustratedin ,'Fig. 6, the selected rangesector being brighter than the remaining portion of the range.Thefbrightening of one sector is produced, as it maybe recalled, byimpressing the rectangular pulses'--l on the intensity grid of tube I4.'This accentuation of the Idesired range sector on the screen of thefull range tube serves as an indication of the sector which isreproduced on the screen of the high velocity tube. No range determiningmeans are provided in connection with theflow velocity tube, becausethis tube is being used for the sole purpose of indicating theapproximate locations and presence of the objects within the exploratorylobe of the transmitting antenna 36. ri'he high velocity tube I6reproduces any one-quarter of the full range, the selection of thequarter sector being accomplished by switching the phase shifter 30 intoone ofthe four possible positions. Upon the selection of the desiredsector, the range measuring circuit 55 is operated until the verticalstep 100, Fig. 7, coincides with the desired echo. rThe range sector`illustrated in Fig. 7 corresponds to the first sector 602 illustratedin Fig. 6, and vertical step 100 was made to coincide with the leadingedge `of an echo 702, thus determining the slant range to the objectproducing this echo.

Referring now to the Figs. 3 and 4, the relationship of which withrespect to each other is illustrated in Fig. 2, the upper portion ofFig. 3 shows the schematic diagrams of square vwave generator I8 andbuffer ampliiier 20, while the lower portion of Fig. 3 shows frequencydivider 22, filter 24, amplifier 23, and phase shifter 30. Themagnetostriction oscillator and shaping amplifier I'I do not appear inFig. 3, since suvfcient references were previously given which fullydisclose these components. Fig. 3, therefore, begins with the conductorI9 which connects the control grid of a triode 300 to the output of theshaping amplifier I'I. In Fig. 4 the full range tube I4 appears in theupper right corner, mixer 28 and sweep circuit 42 in the upper centralportion while the high velocity tube I6, amplier 46, mixer 48, expander50, sweep circuit 52, and the range measuring circuit 56 appear in thelower portion of the figure.

YProceeding now with the description of the circuits shown in Fig. 3,the square wave generator I8 comprises two vacuum tubes 360 and 302connected in a well known multivibrator type circui-t (modiledEccles-Jordan circuit) generating rectangular waves E--L Thismultivibrator is paced by the rectangular pulses 5-0 impressed n thecontrol grid of triode 300 over conductor I9. The oscillograms of thesignals illustrated in the Figs. 3 and 4 also appear in Fig. 5 wherethey are illustrated in their proper time relationship with respect toeach other. The voltage wave -I is impressed on a buffer amplifierpentode 304, and the latter impresses its output 5-2 over aconductor 305and a condenser-resistance combination 306, 308 on a frequency divider22. The frequency divider 22 consists of triodes 3I0 and SI2 connectedas a multivibrator circuit. The circuit of the triodes 3I0 and 3 I2 issimilar to the circuit of the triodes 300, 302 but its parameters areadjusted so as to reduce the frequency impressed upon it by a factor offour. The signals appearing in the output of this multivibratorareillust-rated at 5-3. These are impressed on filter consisting of aplurality ,of condensers 3I4and rcsistances 31.5, the ,time constantsgofwhich rare adjusted to the' fundamental -rrequency'compo nent .of thevoltage wave 5--3 impressed upon them. The sinusoidal wave 5--3appearing in the output of this filter is impressed on a linealamplifier 3I6, the output of which is connected to the control grid ofanother linear amplier 3,22. The plates of these ampliers are connectedover conductors 3I5 and 324 to terminals #l andyz#2 respectively of afour-positioned switch 326, these terminals representing the Zero and.180 phase shift'positions respectively of switch 32.6. The platecircuits of the ampliers SIB and :3.22 are alsointerconnected by meansof resistancecondenser combinations 321-328 and 329-330, which areadjusted so that ,and 270 phase shifts in the sinusoidal wave areobtained fat terminals #2 and #3 of the phase shifter switch 326, thevphase shifts being measured with respect to the Zero phase shiftsinusoidal wave 5-5 appearing at the #l terminal of the switch. A`rotatable arm 325 of phase shifter switch 326 is connected over aconductor 332 to a mixer pentode 402, the function of which will bedescribed later in connection with the description of `the circuitsconnected to the high velocity oscilloscope tube I6. Phase shifter 33,Fig. l, therefore, consists of the triodes 3I6, 322, theresistancecondenser combinations 3271-423, 329-330, ,and four-positionswitch 326, the resistance-condenser combinations remaining fixed oncethey have been adjusted to produce the 90 and 270 phase shifts. Thedescription of the operating cycle of the radio locator will reveal thefact that, although the phase shifter is indispensable in '75% of allrange determinations, it does not ailect the accuracy of the rangedeterminations.

The sweep circuit of the full range tube I4 begins with a pentode 404 inFig. 4, which corresponds to mixer 28 illustrated in Fig. 1. The screengrid of pentode 404 is connected over conductor 303 to the output of thebuffer ampliier 304 so that the pulses 5 2 are impressed on the screengrid of this tube. The control grid of pentode 434 is connected over aconductor 3I'I to the output of the sinusoidal wave amplifier 3I6. Thecombination of signals impressed on the control gridand screen grid ofpentode 404 is illustrated at `5--I2, and the signals appearing in its`plate circuit are illustrated at 5-I3. The pentode is so biased thatall signals except the rectangular pulses which coincide with thepositive crests of the sinusoidal wave are incapable of overcoming theblocking potential of the pentode, thus rendering it periodicallyconductive, as illustrated by the negative voltage waves 5--I3.

The negative pulses 5-I3 are impressed on the control grid of a shapingampliiier M0, the plate circuit of which is equipped with an inductance4I2, a condenser 4I4, and a resistance M6, inductance 4I2 being theelement of this network which controls in the main the form of thesignals impressed on the control grid of the sawtooth generator 4I3. Theplate current varia-.

tions of pentode 4I!) have a substantially rectangular wave form whichthrough inductance produce sharp pealrs of voltage 5-I4 across the coil4I2, the maximum voltage being produced when the rate of change ofcurrent is greatest. During the time represented by the ilat portion ofthe current wave, no voltage is developed in the'inductance, and thevoltage pulse `is reversed whenthe rateof change of current reverses itsSign. Therefore, the voltage waves appearing acrossinductance M2 consist:of aseries oipositirefandnegativepulses-5-I4. l

The other circuit elements of the pulse-generating network are the R. F.by-pass condenser 4M and the damping resistance M6. The capacitance ofcondenser M4 is much too low to resonate inductance M2 to the frequencyof the pulses 5 I3. To prevent this resonant circuit from oscillatingbecause of the occasional shock excitation provided by the pulses 5 i3,it is shunted by the damping resistance 526. Resistor M5 limits thevalue to which saturation current rises and so limits the shockexcitation to the inductance-capacitance circuit with which it is inAseries. The voltage drop across the resistor M5 is not applied to thegrid of the saw-tooth generator tube 438.

The saw-tooth wave generator 4118 is biased beyond cut-01T so that it isaffected only by the positive peaks of the driving voltage v.Fl-Hl. Thesaw-tooth generating condenser 529 being charged slowly through aresistance 42d accumulates its usual charge resulting in the generationof the saw-tooth voltage wave 5 l5. When the positive peaks of thedriving voltage 5 14 appear on the control grid of pentode i I 8 it isrendered fully conductive, thus discharging condenser 132i). Thesaw-tooth wave 5 l5 is impressed in conventional manner by means of acondenser 422 and a resistance 32d on the horizontal deection plates oftube I4. The discharge time of condenser 420, which represents thereturn cycle of the electron beam, is so short that it is usually notdiscernible on the screen. Several sweep amplifying stages, which areordinarily interposed between condenser llZll and cathode tube it, arenot illustrated in Fig. 4. The vertical plates of the tube are connectedin conventional manner to the output of receiver l2, Fig. 1, over aconductor 426 and a coupling condenser Q23. The same type of couplingalso exists between the vertical plates of the high velocity tube i6 andthe receiver.

From the description of the circuit of the full range tube, and the timerelationship of the signals illustrated in Fig. 5, one may readly seethat the generation and timing of the saw-tooth Wave 5 I5 is undercontinuous control of the leading edges of every fourth rectangularpulse 5 2 selected by mixer lille, the latter 'transforming them intothe pulses 5 i3. It is to be noted that the above mentioned leading edgeof the rectangular pulse does not initiate the charging period of thecondenser, but is used for generating strong, driving pulses 5 l It, thepositive peaks of which are used for discharging the saw-toothgenerating condenser 429. Because of the low impedance offered bypentode lili! when it is rendered fully conductive by the pulses 5 l4the discharge period of the condenser 420, as mentioned previously, isextremely rapid and takes place during the transmission of theexploratory pulse 5 16. Depending upon the timing of the circuits of thetransmitter and the length of the exploratory pulse, it may or may notappear on the screen of the low velocity tube. If the duration of theexploratory pulse is relatively long, the lagging portion of it, Sill,Fig. 6, may appear at the extreme left portion of the horizontal sweep.irrespective of the parameter of the circuits of the transmitter and ofthe sawtooth wave generator M3, the non-appearance or the appearance ofthe transmitted pulse till on the screen of the full range tube ll hasno detrimental effect on the operation of the radio locator since thefull range tube is used only for the reproduction of the full range eldrather than actual range determinations. Accordingly,- the onlyrequirement that must be satisiied in connection with the full rangechannel resides in the fact that all echoes appearing directly after theexploratory pulse are faithfully reproduced on the screen of the fullrange tube.

The high velocity tube channel begins with mixer MP2, the screen grid ofwhich is connected over conductor 333 to the output of the bufferamplifier and the rectangular pulses 5 2. The control grid or" mixer d2is connected over a conductor 322 to the adjustable arm 325 of thefour-position switch. 25, this connection impressing the sinusoidal waveon this grid. The phase of the impressed sinusoidal wave is determinedthe particular position of the adjustable arm 325 on the four contactsof the switch. The combined signals impressed on the control and thescreen grids of pent-ode lill are illustrated at 5 5. Examination of thephase relationship between the sinusoidal waves 5 1 and 5 5 indicatesthat the adjustable arm 325 is making contact with #l terminal sincethere is no additional phase shift introduced between the sinusoidalwaves 5M and 5% except the usual phase inversion which takes placebetween the input and the output circuits of a vacuum tube. As in thecase of the previously described mixer i355, mixer 15..'2 is so biasedthat only the rectangular pulses which coincide with the positive crestsof the sinusoidal waves render mixer lil? conductive. Because of therelatively large time constant of the resistance-condenser combination3il 432 the rectangular pulses selected by mixer 352 appear as distortedsignals 5 6, and these are impressed on an expander-amplifier pentode434. Pentode i3/3 is normally fully conductive, and the negative signals-t overdrive it in the negative direction so that the positive voltagesignals appearing at its plate are substantially rectangular voltage'pulses 5 i. The amplitude as Well as the degree of distortion producedby the R-C network 3ll l32 are such that the distorted signals 5 6render pentode LEGS fully non-conductive for a period equal to theperiod of the rectangular pulse 5 2, as illustrated in Fig. 5. Thesubstantially rectangular pulses 5 1 are irnpressed on aninverter-amplifier pentode $36 which reverses the sign and improves theform of the driving signals by converting them into substantiallyrectangular pulses 5 These are impressed on the control grid of atetrode A38 which, together with a condenser dell and resistanees lilland 4t2, acts as a saw-tooth generator. Resistance lili! is used forregulating the waveform of the saw-tooth wave generated by condenserMib.

Tetrode S38 is so biased that it is normally fully conductive, thuskeeping condenser fidi? normally in discharged condition. To impart thenecessary stability to the saw-tooth generator circuit during these longconductive periods, the screen grid of tetrode itil is connected toground through a voltage regulator gas-filled tube M6. Since the highvelocity tube It is used for all range determinations, and the rangemeasuring circuit is connected and controlled by the sawtooth wave 5 91,the starting point of the horizontal sweep, which is the plate potentialof tetrode 438, must remain constant during the conductive periods ofthis tube. To improve the stability of tetrode i338 its screen grid isclamped clown by the voltage regulator ttt.

The negative rectangular Wave 5 8 impressed on the control grid oftetrode i158 renders it nonconductive, and during this non-conductiveperiod the saw-tooth generating condenser 446 has its charging periodthus generating a sawtooth wave 5 9. The duration of the linear portionof the saw-tooth wave 5 9 is equal to the period of the rectangular wave5 2, and it is this mode of timing of the saw-tooth generator thatenables one to reproduce on the screen of the high velocity tube l5 onlyone quarter of the full range. It may be recalled that the duration ofthe linear portion of the saw-tooth wave 5 5, which acts as the fullrange base line, is equal to the four periods of the rectangular wave 52; similarly, the transmitted pulses 5 6 are spaced four rectangularpulses apart.

rlhe intensity grid 54 of tube I6 is connected to a rheostat 435generating the positive rectangular voltage wave 5 1. Tube I6 isnormally so biased that none of the signals are reproduced on itsscreen, and it is only during the appearance of the positive voltageWave 5 1 on its intensity grid 5 4 that it is capable of reproducing anyecho signals. The same type of connection, but at a lower point on therheostat, exists between the intensity grid 44 of tube |4 andpotentiometer 435, this connection intensifying the brightness of theselected sector 502, Fig, 6, on its screen.

The range measuring circuit itself consists of diodes 443, 456, triodes452, and 454, and a potential divider circuit 456, 451, and 458. A moredetailed description of a preferred form of potential divider circuitmay be found in a patent application Ser, No. 470,413 of James R. Mooretitled Resistance Network and iled on December 28, 1942, now Patent No.2,423,463, issued July 8, 1947. A source of positive potential 458 isconnected to ground 451i through the. potential divider, and to thecathode of diode 448 through the fixed resistance 456.

The plate of diode 448 is also connected to the positive source ofpotential 460 through a plate resistor 442. When condenser 440 beginsits charging period, diode 448 is non-conductive since the positivepotential impressed on its cathode over resistance 456- is higher thanthe potential appearing at the upper plate of condenser 440, which is atapproximately ground potential when tetrode 438 is fully conductive.However, when tetrode 438 is rendered non-conductive, and as thepotential across condenser 440 begins to exceed the potential impressedon the cathode of diode 448 through resistor 456, diode 448 becomesconductive and remains conductive until the negative potential impressedon the control grid of tetrode 438 is removed at the lagging edges ofthe rectangular waves 5 6, and condenser 440 begins to discharge acrosstetrode 438. At this instant the potential impressed on the plate ofdiode 448 drops again to a very low value, and diode 448 becomesnon-conductive once more. The instant when diode 448 becomes conductivemay be varied by varying the setting of the rheostat arm 46|. When thisarm is set near ground 459, diode 448 becomes conductive with thebeginning of the charging period of condenser 440. Conversely, when thepotentiometerarm 46| is moved to the left, and nearer to the source ofthe positive potential 456, there is a delay period between the timecondenser 440 begins its charging period and the instant diode448becomes conductive. denser 462 and a resistance 464 to the controlgrid of a triode 452 thus controlling its conductivity. The cathodes ofthe triodes .4.5.2.aI1r:l.f..45|Lr Diode 448 is connected through acon--l are connected to ground through a common cathode. resistor 414,and the plate of triode45-2is.- connected to the cathode` of diode 453.through a. The cathode andthe coupling condenser 45|. plate of diode 450are connected to ground atf410 through resistors 41| and 412respectively,;and-

resistor 412 is shunted by a condenser 413-. The

of diode 45B.

and 466.

denser 418 and a conductor 416. may be connected either to the verticalor horizontal plates of the oscilloscope, depending4 upon7 the desiredtype of marker indication.

With no negative rectangular wave 5 8 im; pressed on tetrode 438,triodes 452 and 454'are. equally conductive, their cathodes bei-ngcork,y nected to ground 414 their plates tothe common. source ofpositive potential through the `equal resistors 419 and 486, and thegrids grounded through the grid resistors 464 and 412, the con'-Adensers 462 and 413 exerting. no influence onv the respective controlgrids at this time. instant condenser 462 is charged to a steady' state.potential determined by the setting of the potentometer arm 46|. deredconductive, condenserV 462 becomes oonnected to a higher positivepotential through dif ode 448 and there is an instantaneous. surge otrcharging current into condenser 462 through; grid resistor 464 whichrenders the. control grid of triode 452 more positive and triode 452morecon' ductive. This results in such a lowering of potential impressedon the cathode of diode 45D,

Connected between the plate` of.l triode 452 and,` The- R-C networks 41|45I and 412 413.` of diode-- ground 41D, that it is rendered conductive.

450 keep it conductive for the remaining portion of the saw-tooth wave.When diode 450 is, rendered conductive, it impresses a negative po.-tential on the control grid of triode 454 rendering triode 454nonconductive. The negative potential impressed on the control grid oftriodev 454 and the resistance drop across resistance `414 keep triode454 nonconductive as long as triode 452 is conductive. When diode 448 isrendered nonconductive, which takes place during the discharge period ofcondenser 44|), triode 452 is rendered momentarily nonconductive,because at this instant condenser 462 adjusts itself to.` a lowerpotential impressed upon it across a circuit composed of ground 453,rheostat 45B, resistor 451, condenser 452, and grounded resistor 464'.

During this instant the excess of electrons onf the right plate ofcondenser 452 leaks oi through resistor 464, rendering triode 452momentarily nonconductive. The time constant ofthe condenser 452 is verysmall so that condenser 462' is capable of adjusting itself to thesteady state potential very quickly. It should be noted that' thisadjustment period of condenser 462 coincides in time with the returncycle of the cathode. ray beam in tube I6, which is sup-pressed by theintensity grid 54. When triode 452 becomes nonconductive, and aftercapacitor 413 has dis charged through resistor 412, triode 454becomes4conductive since there is momentarily no potential drop over resistance414 and the negative po tential impressed on its grid is removed after'condenser 413 discharges to ground throughl re'- When this. is the case,the control@` sistor'. 412i,

At this.l

When diode 448 is, ren.-I

13 grid of triode 454 and its cathode are both at ground potential, andtriode 454 is rendered conductive. During this brief period diode 450acts as decoupling means between the plate of triode 452 and the grid oftriode 454.

When condenser 452 assumes once more its steady state potential, thetriodes 452 and 454 become equally conductive again, as describedpreviously. The cycle repeats itself with the repetition of the chargingand discharging cycles of condenser 440.

From the description of the range-determining circuit, it follows thatthe setting of the potentiometer arm 45E determines that instant of timewhen triode 454 is rendered nonconductive, thus generating therectangular voltage wave 5-I0 in its plate circuit. It is this positivevoltage wave that is impressed either on the horizontal or the Verticalplates of the high velocity tube I5 over conductor 416, thus producingthe vertical step 100, Fig. 7. The resultant signal impressed on thehorizontal plates of tube l5 when conductor 416 is connected to thehorizontal plate is shown at 5-ll in Fig. 5. As indicated by thedoubleheaded arrows at 5-10 and 5-Il, the time of occurrence of theleading edge of the rectangular Wave 5 il may be varied, so that thismarker step may take place at any time along the linear portion of thesaw-tooth wave 5 9, this variation being obtained by varying the settingof the potentiometer arm 45|. It thus may be aligned with any echo, andwhen this is accomplished, the rheostat setting at once gives the slantrange distance in linear units to the object producing the selectedecho.

This type of range determining circuit is being claimed in my copendingapplication, Serial No. 467,261, led November 28, 1942, which disclosesanother species of this type of circuit.

One of the factors influencing the accuracy of range determinations iswhether step 100 is produced with such speed that it appears as avertical or as a slanting line on the screen. Since the Vertical stepmay be aligned more accurately with an image of an echo than theslanting step, it becomes very desirable for it to be vertical. This isthe case because of the action of the diodes 446 and 450, cathoderesistor 474, and the amplifying action of the triodes 452 and 454. Whendiode 448 is rendered conductive, there is a Very rapid rise in the gridpotential of triode 452 and simultaneously rapid rise in theconductivity of triode 452. This rise in the conductivity of triode 452is accentuated by the fact that triode 454 is rendered nonconductivebecause of the instantaneous IR drop in the grid resistor 412. Whentriode 454 is rendered nonconductive, it reduces the IR drop acrossresistance 414, thus depressing the cathode of triode 452. This resultsin the regenerative action between the triodes 452 and 454, the formerbecoming fully conductive and the latter fully nonconductive. For thesereasons, triode 454 may be considered to become nonconductiveinstantaneously, and the step 100 actually appears as a vertical step onthe screen of tube i6 in spite of the fact that tube l5 uses the highvelocity sweep.

It should be noted that when diode 448 becomes conductive, the timeconstant and the effective resistance of the charging circuit ofcondenser 440 will have a slightly different value than during itsinitial charging period, the latter being controlled solely by theresistances 442 and 44|. When diode 4148 becomes conductive, theparameter of the charging circuit changes, and this may produce a slightchange in the rate of charging condenser 440. This change, however, willnot alter the accuracy of any range determinations because all rangedeterminations are controlled by the condition of the circuits duringthe period of time which precedes this change.

It has been previously mentioned in the speciiication and in the objectsof invention that the accuracy of range determinations is not affectedby the error produced by the phase shifter. When all rangedeterminations are performed by means of phase shifters, the phaseshifters must of necessity be an adjustable type so that smooth,continuous phase displacement may be obtained from 0 to 360. It is thistype of phase shifter that has an accuracy of approximately i3%. In thedisclosed system the phase shifter is of step-bystep type, and in thespecific example only 0, 90, and 270 phase displacements are available.These steps may be adjusted so as to give much greater accuracy thanm30/b. Accordingly, While the error in shifting phase of the sinusoidalwave 5-4 by the phase shifter te, Fig. 1, is much less than 3%, even ifone is to assume that, because of instability of the components of thephase shifter, there is an error as large as 6%, even then this errorWill not affect the accuracy of the range determinations since theaccuracy depends solely on the accuracy of the potentiometer circuit45t, 45?. That this is actually the case may be perceived fromexamination of the signals illustrated in Fig. 5. The range measuringcircuits, the sweep, and the transmitter circuits are all timed andcontrolled either by the pulses 5-6 or 5-i4, and the timing of thesepulses is not affected by any slight changes in the timing or phasing ofthe sinusoidal waves 5 5 and 5-12. The signals illustrated at 5-5 and5-i2 are im# pressed on the mixers which are so biased that only therectangular pulses which coincide with the positive crests of thesinusoidal Waves get through the mixers, the remaining signals beingsuppressed. lt is apparent that so long as the timing of the sinusoidalwaves is only approximately correct, proper rectangular pulses will beselected, and, since the subsequent control of the circuits is allaccomplished by the leading edges of the selected rectangular pulses,the errors produced by the phase shifter will have no effect on therange determinations. This may also be apparent from the connectionsillustrated in Fig. 1, where the output of buffer amplifier 2i? isconnected to mixer 28 over conductor 29, and to mixer 48 over conductor35. The rectangular pulses 5--1 impressed on these mixers will beselected by the mixers irrespective of slight changes in phase of the'sinusoidal waves, also impressed on the mixers, so long as the mixersare properly biased, and so long as the amplitude of the rectangularpulses 2i is sufficiently high to overdrive the mixers even when thescreen grid voltages change slightly because of minor variations in thephase of the sinusoidal waves.

Referring now to Fig. 8, it discloses one type of mechanical connectionbetween the phase shifter 30, Fig. 1, and the range measuring circuit55, which enables one to obtain all range readings on one dialirrespective of the setting of the phase shifter. The advantage of sucharrangement is that the probability of obtaining erroneous rangereadings is reduced to a minimum since the range reading appears on asingle dial as a single, cornplete range reading, and the range operatordoes not have to pay any attention to the setting of the phase shifter.The arrangement consists of all accerti metal'box' provided with a cover802, the' latter beingequipped with a slit E63. Two brackets, 804'andBG, are mounted on the lower panel of" box 8B,.these brackets actingas mechanical supports for shafts Sand 8H). Rigidly attached to shaft808 are the phase shifter arm 325, a Geneva gear sector 812, and a rangedial scanning shield 8M. The phase shifter arm 325 is connected toconductor 33'2 and makes Contact with a commutating segment 8|3, whichis equipped with four metal contacts #1, 2, 3, and fl. These corre spondto the similarly numbered contacts ofthe phase shifter switch 326illustrated in Fig. 3. The four wires. 315, 3&9, 32, and 324 correspondto the similarly numbered conductors in Fig. 3 Which connect thefour-position switch 32S to the triodes GIS. 322 andresistance-condenser combinations 329-330 and 3217-328' interconnectingthe plate circuits of these triodes. Accordingly, segment 816' and arm325 represent the phase shifter switch 32B illustrated in Fig. 3.

The rheostat arm Alti, which corresponds to thelsimilarly numberedrheostat armofA the range measuring circuit shown in Fig. 4, is rigidlyconnected to shaft SIU. Also rigidly connected tol shaft 8 I l) is agear B i8 which represents the driving gear of the Geneva intermittentmotion arrangement interconnecting the shafts 8m' and 808.. A rangewheel 822, also rigidly connected to shaft 820, is used for aligning thevertical step 700, Fig; 7, with the desired echo. The rheostat arm 461'makes contact with the rheostat 958, which corresponds to the similarlynumbered rheostat in Fig. 4 used for the actual range deter` minations.In the position illustrated in Fig. 3, thescanning shield 814 ispositioned so that its scanning' perforation 824 is in line with slit863 and the outer scale appearing on the range dial disc 820; this scaleis calibrated from Zero to 50 miles, should the full range of the systembe equal 1:01200 miles. The succeeding scales of disc 829) arecalibrated respectively to give range readings from 50 to 100, 100 to150, 150 to 200 miles, and the scanning sector lcl is provided with theadditional three perforations 325, 826, and 821. These p'erforationsbecome positioned in line with their respective scales and slit 803 whenthe range wheel 822i is turned sufcient number of revolutions toaccomplish this result.

When the clockwise-rotated driving gear 8&8 engages' with its tooth S28a recess 330 of sector 8t2, the latter is turned through a limited angleina counter-clockwise direction, turning shaft- U, scanning sector li,and the phase shifter arm 3255 through the same angle. Phase shifter arm325 now makesI contact with #2 terminal, whilel thev scanning sector 81Maligns perforation" B-With the slit 8e3, thus obliterating allrangevscales except the range scale from 5G to 100 miles'. The sainetype of intermittent turnin'gof shaft SGS takes place when driving geartvre'aches'recesses 83| and 832, thus succes-Y sively turning' the.rangel armi from #2 terminalto'` #3- and4 #4. terminals. Upon reachingthe maximumrange, the range determining assem` bly may be returned againto its original zero range position by turning the range wheel 822 ina--countereclockwise direction.

The advantages of the arrangement illustrated in Fig. reside in the factthat the shafts 8l@ and 8081 areI interconnected through theintermittent motion Geneva gears 818 and BIZ which enable one to alignthe desired scale with the:

perforationsof sector 814 and slit 3f03- andlobliterateall-other scales,thus positively prevent-` i'ngany confusion which could otherwise'.exist. Moreover; the range-determining rheostat- 458 and the phaseshifter arm 325 are operated by thevsame wheel 822, the operation ofthese elements being so synchronized that the phase shifter arm isturned to the next terminal upon the completion of the elective turn ofthe rheostat arm 46|. The rheostat 458 is so woundr that one of itssectors, at the end of the rheostat, is provided with a low resistanceconductor which does not produce any change in the resistance setting.This sector, as Well as the potentiometer arm 461, is aligned with thetooth 828 of the driving gear 318, so that when tooth 828 begins to turnshaft 888, the rheostat arm 451 travelsalong'the low resistanceconductor, thenV connects this conductor to ground by bridging the gapbetween the two extremesl of the rheostat, andy finally finds itselfpositioned at the zero resistance position of the rheostat. Thus asmooth transition from one selected sector. to the next is obtainedwithout any undue disturbance of the rangeV measuring circuits connectedto this rheostat.

The operation of the system should be apparent from the descriptiongiven thus far, and for this` reason, only a brief summary of itsfunctional cycle will be given here. The entire fieldscanned by thetransmitted exploratory pulses 5--l5 continuously appears on the screenof the full range oscilloscope tube It. The operator chooses the desiredsector for its reproduction on the screen of the high velocityoscilloscope by observing the position of the desired echo on the screen0f the full range oscilloscope. The screen is provided with the sectormarkings so that the operator is at once in a position to determine thenumber of the sector in which the selected echo lies. The selectionis-performed by operating wheel 822 of the range measuring circuit, theselection being at once indicated on the screen of the full rangeoscilloscope by brightening of the images of the echo signals whichappear in the selected sector. After this selection of the desiredsector the operator adjusts the rheostat arm 46| of the range measuringcircuit which aligns the vertical step 10U with the image of theselected echo on the screen of the high velocity tube. The range readingmay then beobtained by noting the reading of dial 820.

From ther description of the radio object-ldr eating system, andparticularly the methodand apparatus forv determining slant ranges ofivthe object detected'by this system, it should be ap"i parent that itoffers definite advantages since it enables one to make rangedeterminations with a much greater accuracy than it `hasbeen possibleheretofore with the systems of thistype'.v

The invention hask been illustrated anddes'cribed` in connection withthe systemV where the ratio between-thev frequencies of the wavesgenerated by' the square wave generator 53' and the sinus4` oidal waveappearing in the output of lter 24 is 4 toi l ratio. The accuracyrequirements, as a rule, are very Well satisfied when this ratio ofifrequencies is used, but it is obvious that the system is not limited tothat speciiic ratio, and when the accuracy of range determinations maybe'` either lower or higher, the above frequency ra'- tio may be changedto conform with the soughtresults. When higher accuracy is desired the'frequency of the master oscillator must be in creased Withthe frequencyof the frequency divider remaining. constant. I

It should be noted that -while'in the schematic diagram shown in Figs. 3and i some speciilc circuits were illustrated which perform thenecessary functions, it should be obvious to those skilled in the artthat these specific circuits may take different, known forms; forexample, the frequency divider circuit and the filtering arrangementsillustrated in Fig. 3 may be replaced with the shock excitedoscillators, or many other frequency reducing circuits which. arecapable of performing the same function. The same is true of the sweepchannels for the high and lov,r velocity oscilloscope tubes, thecircuits used for this purpose may be replaced with other welt-knownsweep generating circuits which perform the intended function with equaleffectiveness.

vthe generated saw-tooth waves possess highy clegree of linearity, theresistance network may be an ordinary linear rheostat. The multivibratorcircuit 39E-2h32 may be of that type where both tubes are controlled bythe signals from the master oscillator.

It is believed that the construction and operation of the radio locatorand range determining circuits will be apparent from the foregoingdemaster oscillator, a frequency dividing circuit i connected to saidmaster oscillator, a filter connected to the output of said frequencydividing circuit and adjusted to the fundamental wave of said frequencydividing circuit whereby its output is a substantially sinusoidal wave,an ampliiier and a phase shifter connected to the output ci said lter,and a mixer connected to said master oscillator and said phase shifter,said mixer selecting only that series of pulses generated by said masteroscillator which coincide in ,i

time with the positive crests of the wave impressed on said mixer bysaid phase shifter, ,and a multicontact switch interposed between saidphase shifter and said mixer for selecting the phase of said sinusoidalwave, said phase positions differing from each other by stepscorresponding to a 360 phase shift of the wave generated by said masteroscillator.

2. A radio object-locating system including a receiver, a full rangeoscilloscope and a high ve'ocity oscilloscope connected to saidreceiver, a series circuit including a master oscillator, a shapingamplier, a square wave generator synchronized with said masteroscillator, a frequency divider, a filter tuned to the fundamentalfrequency of said divider, an amplier, a phase shifter and a mixer; saidmixer being also connected to said square Wave generator whereby saidmixer is rendered conductive by a selectable series of pulses generatedby said square wave generator, the selected series being determined bythe setting of said phase shifter, an expander connected to said mixer,a sweep generating circuit connected on its input side to said expanderand on its output side to said high velocity oscilloscope, said sweepcircuit being synchronized with said master oscillator through saidseries circuit, expander and mixer, a range-measuring circuit connectedon one side to said sweep circuit and on the other side to said highvelocity oscilloscope,

said range-measuring circuit generating an adjustable marker signal; asecond mixer connected to said amplifier and to said square wavegenerator, said second mixer selecting a fixed series of pulsesgenerated by said square wave generator, a pulse-shaping aniplierconnected to said second mixer, and a second sweep-generating cir'- cuitconnected on its input side to said pulseshaping amplifier and on itsoutput side to said fui-l range oscilloscope.

3. A radio object-locating system including a rst multivibratorgenerating a first series of pulses, a buffer amplifier connected tosaid rst multivibrator, a second multivibrator connected to said bufferamplier, said second multivibrator representing a frequency dividingcircuit reducing the frequency impressed upon it by a factor of four, alter connected to said second multivibrator tuned to the naturalfrequency of said second multivibrator, an amplifier connected to theoutput of said filter, a multigrid mixer tube connected with one controlgrid to the output of said amplifier and with the other control grid tothe output of said buffer amplifier, said mixer tube selecting everyfourth pulse generated by said first multivibrator, and a sawtoothgenerating circuit connected to said mixer tube, said circuit generatinga sawtooth Wave, the duration of the linear portion of said wave beingapproximately equal to the time elapsing between the leading edges ofthe pulses selected by said mixer tube. y

4. A radio object-locating system as donned in claim 3, which furtherincludes a keyer and a transmitter, said keyer being connected to theoutput of said mixer tube, whereby said keyer is controlled by thepulses selected by said tube.

5. A radio object-locating system as defined in claim 3, which furtherincludes a pulse-shaping differentiating network between said mixer tubeand said sawtooth generating circuit, said differentiating networktransforming the pulses selected by said tube into positive and negativepulses, and connections between said differentiating network and saidsawtooth generating circuit for timing said sawtooth generating circuitby means of said positive pulses.

6. A radio object-locating system as defined in claim 3, which furtherincludes a transmitter, a keyer connected to the output of said mixertube, said tube controlling through said keyer transmission ofexploratory pulses by said transmitter, a receiver, and a cathode-raytube connected to said sweep circuit and said receiver, saidtransmitter, receiver, and sweep circuit being so constructed andarranged that said cathode-ray tube reproduces on its screen all signalsreceived by said receiver during the intervals of time between saidexploratory pulses.

7. A radio object-locating system including a series circuit of a rstmultivibrator, a first buffer amplifier, a frequency dividing secondmultivibrator reducing the input frequency in a Ii-to-l ratio, a filterhaving its parameters adjusted to the natural period of the wavegenerated by said second multivibrator, a second buffer amplifier, aphase shifter providing 0, 90, 180 and 270 phase displacements of thewave appearing in the output of said second buffer amplifier, afourcontact switch, and a multi-grid mixer tube connected to saidcontact switch with one control grid and to the output of said firstbuier amplier with the other control grid, said mixer tube selectingevery fourth pulse generated by said first multivibrator, and means foroperating said 19 switch from one contact to the next for making saidmixer tube select a pulse generated by said rst multivibrator adjacentto the previously selected pulse.

8. A radio object-locating system as dened in claim '7, which furtherincludes a second Vseries circuit of a pulse-shaping network, anamplifier, and a sawtooth generator connected to said mixer tube, saidsecond series circuit being so constructed and arranged that theduration of Vthe linear portion of the sawtooth wave generated by saidsawtooth generator approaches the duration of one full period of thewave generated by said rst multivibrator.

9. In a radio object-locating system, a range measuring unit including afirst shaft, an adjustable resistance network, a calibrated range dial,said network and said dia-l being rigidly connected to said rst shaft,al second shaft, aphase shifter, a commutator segment connected with itsconductive segments to said phase shifter, a revolvable arm makingcontact With said segment and rigidly connected to said second shaft,and in*- termittent motion means interconnecting said iirst and secondshafts.

10. In a radio object-locating system as defined in claim 9 in whichsaid range-measuring unit further includesa front panel With a slit, anda scanning sector rigidly mounted on said second shaft, said scanningsector being provided with a plurality of scanning openings alignablewith said slit and said dial.

11. In a radio object-locating system as defined in claim 9 in whichsaid range-measuring unit and said intermittent motion means furtherinclude a driving gear, and a Wheel for operating said unit, saiddriving gear and said wheel being rigidly connected to said rst shaft.

12.` In a radio object-locating system as defined in claim 9 in whichsaid intermittent motion means comprises Geneva gears, said Geneva gearstransferring said revolva'ble arm from one'con'- ductive segment to thenext for each revolution of said rst shaft.

13. A range-measuring unit including 'cyli'ndrical rheostat, ana-xiallymolnted adjustable rheostat arm revolvable' through 366% a phaseshiftery a multipo'sition :mitchV connected to `said phase shifter, aplurality of contacts onY said switch, and intermittent motion meansinterconnecting said arm and said switch, said intermittent motion meansbeing so constructed and arranged that said switch is moved from onecontact to the next -when said rheostat arr'n is turned so as to makecontact with the'minimum resistance point and to break contact with themaximum resistance point on said rheostat;

14. A wave-shaping amplier including rst and second vacuum tubes, saidtubes each having a cathode, at least one control grid, and a plate; a`ycommon cathode resistor connecting the cathodes of said tubes toground, a source of potential grounded with its negative pole andconnected with its positive pole to theplats of said tubes throughindividualplate resistors. adiode having a plate and acathode', aresistor and a condenser connecting the cathode of said diode to groundand to the plate of said first tube respectively, a direct, metallicconnection between the plate of said diode and the control grid of saidsecond tube, a -condenser shunted by a resistance connecting saidmetallic connection to ground, an input circuit connecting the' controlgrid of said rst tube to asource of varying potential,- and an outputcircuit connected to the plate of said second tube.

JAMES R. MOORE.

References Cited in the flle of this patent NITED STATES' PATENT-sNumber K Name4 jate 2,145,332 Bedford Jari.. 31, 1939 L2,225,046 HunterADec. 1'1, i940 2,338,646 Kessler Jan. 4, 1944 2,355,363 christaldi Aug.3, 1944 2,403,626 Wonr July 9, 1946 2,405,233 Seeley Aug. 6, 19462,403,414 Donamson o0t. 1 1946 2,454,732 De Rosa Nv. 30, 348 2,455,265Norgaard Nov. 3o, 1943 FOREIGN PATENTS Numberh n Country Date 552.072Great Britain Mar. .22, 1943

